The present invention relates to a control apparatus for controlling the amount of intake air into the engine in accordance with a leakage in a blow-by gas passage.
It is known that a control valve, which is disposed in an intake manifold connected to an internal-combustion engine (hereinafter referred to as an “engine”), is clogged with carbon (it may be referred to as carbon deposit) with years of use due to deposition of lubricating oil and combustion products.
Japanese Registered Utility Model Publication No. 2558153 discloses a scheme for correcting the amount of intake air in accordance with the degree of clogging of a bypass valve that is disposed in a passage that bypasses a throttle valve.
According to the scheme, a valve for increasing/decreasing the amount of intake air is additionally provided in the bypass passage. At a first desired engine rotational speed, an opening degree D1 of the bypass valve when the additional valve is in a closed position and an opening degree D2 of the bypass valve when the additional valve is in an open position are learned. If the additional valve is closed when the opening of the bypass valve is fixed to D2, the engine rotational speed decreases. The additional valve is then opened to learn an opening degree D3 of the bypass valve. A characteristic of the intake air amount with respect to the opening degree of the bypass valve is updated so that changes in the intake air amount when the opening degree of the bypass valve changes from D1 to D2 are equal to changes in the intake air amount when the opening degree of the bypass valve changes from D2 to D3. Thus, accuracy of controlling the intake air amount is improved by updating the characteristic of the intake air amount.
On the other hand, blow-by gas may leak from a combustion chamber to a crankcase of the engine. There is a conventional scheme for returning the blow-by gas into an intake air system of the engine so as to prevent emission of such blow-by gas to the atmosphere. Japanese Patent Application Unexamined Publication (Kokai) No. 2002-130035 discloses a scheme for detecting a leakage (including disconnection and hole) of a passage that is designed to return the blow-by gas into the intake air system. According to the scheme, if a difference between the amount of air that is actually introduced into the engine and a desired amount of intake air that is calculated by a control unit exceeds a predetermined value, it is determined that a leakage has occurred.
According to the conventional scheme, when the intake air amount increases due to a leakage in the blow-by gas passage, it may be erroneously determined that clogging of the control valve disposed in the intake manifold has been eliminated. The characteristic of the intake air amount may be inappropriately updated. After the leakage of the blow-by gas passage is repaired, control of the intake air amount may start based on such inappropriate characteristic of the intake air amount. This may cause instability in the operating condition of the engine.
If the characteristic of the intake air amount is updated immediately after a leakage occurs, it is determined that an actual intake air amount into the engine has converged to a desired intake amount. Such updating eliminates a difference between the actual and desired intake air amounts, which may make it difficult to detect the leakage.
Thus, there exists a need for a control apparatus that is capable of prohibiting updating the characteristic of the intake air amount if a leakage is detected in the blow-by gas passage. There also exists a need for a control apparatus that is capable of adjusting a speed of updating the characteristic of the intake air amount so as to ensure detection of a leakage in the blow-by gas passage.